(1) Field of the invention:
The invention relates to valves for chamical containers wherein the valves are used for withdrawing liquid or gaseous chemical products from the containers while at the same time supplying a protective gas thereto.
(2) Technical consideration and prior art:
The substances required for the manufacture of semiconductors are predominantly toxic and/or aggressive. Accordingly, impurities in the containers which are used for the storage and transport of these substances, and/or in connected doping and epitaxial plants, can lead to considerable problems in processing procedures and must therefore be excluded. For such applications, valves comprising valve housings with bores therethrough are connected to inlet and outlet ports and controlled by valve spools are used. With such arrangements a protective gas, such as an inert gas, is used to transport the liquid or gaseous products to be withdrawn and in most cases is also used for flushing the connected lines after a withdrawal.
In fiber optic technology, acid chlorides are despatched from and stored in glass containers or, particularly for silicon tetrachloride, stainless steel vessels are used. While steel ball valves are normally used for the stainless steel vessels; for glass vessels, plug valves are used which certainly offer the possibility of flushing with a protective gas, but which often do not achieve adequate sealing on account of relatively low surface pressure at the valve. Other glass and/or PTFE valves are also used for applications of this type.